Wind turbine drive train test assembly

ABSTRACT

One aspect of the invention is a test assembly comprising a prime mover, an actuator assembly and a torque transfer coupling. The actuator assembly has an end configured to be attached to a shaft of a portion of a test specimen such as a wind turbine assembly. The actuator assembly has a shaft supported for rotation by hydraulic bearings. The torque transfer coupling connects the primer mover to the actuator assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/230,318, filed Jul. 31, 2009, U.S. ProvisionalPatent Application Ser. No. 61/252,884, filed Oct. 19, 2009, and U.S.Provisional Patent Application Ser. No. 61/306,160, filed Feb. 19, 2010,all of which are hereby incorporated reference in their entirety.Incorporated herein is also US patent application entitled “TORQUETRANSFER COUPLING” having Ser. No. ______ and filed even date herewith.

BACKGROUND

The discussion below is merely provided for general backgroundinformation and is not intended to be used as an aid in determining thescope of the claimed subject matter.

FIG. 1 schematically illustrates a wind turbine assembly 10 and a hubcoordinate system used to define forces and moments experienced by thewind turbine assembly 10. The wind turbine assembly 10 will be subjectedto various loads (forces and moments) when in operation, for example butnot limited to a difference in wind speeds from wind above the windturbine assembly and wind closer to the ground/water surface as well asvarious forms of wind gusts. The forces and moments can be defined withrespect to three orthogonal axes (X, Y and Z) as an axial force F_(X),radial forces F_(Y), F_(Z), shaft torque M_(X), and moments about radialaxes orthogonal to the shaft axis, i.e. M_(Y), M_(Z). These loadstypically are of different magnitudes and different frequencies, but areapplied simultaneously to the wind turbine assembly 10.

SUMMARY

This Summary and the Abstract herein are provided to introduce aselection of concepts in a simplified form that are further describedbelow in the Detailed Description. This Summary and the Abstract are notintended to identify key features or essential features of the claimedsubject matter, nor are they intended to be used as an aid indetermining the scope of the claimed subject matter. The claimed subjectmatter is not limited to implementations that solve any or alldisadvantages noted in the background.

In a first embodiment a test assembly includes a prime mover and anactuator assembly having an end configured to be attached to a testspecimen shaft of a test specimen, where the actuator assembly alsoincludes a shaft. A first plurality of hydraulic bearings is configuredto support the shaft of the actuator assembly for rotation. A torquetransfer coupling is connected to the primer mover and to the actuatorassembly.

In a second embodiment a test assembly includes a prime mover and anactuator assembly having an end configured to be attached to a testspecimen shaft of a test specimen, the actuator assembly also includeshaving a shaft. The shaft of the actuator assembly has a circumferentialsurface and first and second annular surfaces that are disposed inplanes arranged to intersect with a rotational axis of the shaft. Afirst plurality of hydraulic bearings is configured to support the shaftfor rotation about the rotational axis. A second plurality of hydraulicbearings is configured to engage the first annular surface, while athird plurality of hydraulic bearings configured to engage the secondannular surface.

The first and second test assemblies can include one or more of thefollowing features. For instance, the actuator assembly can include asupport structure for supporting each of the hydraulic bearings andactuators connected to the support structure and arranged to applyforces and/or moments to the input shaft. In another embodiment, thehydraulic bearings can comprise a plurality of bearing elementassemblies disposed circumferentially about the shaft. If desired, eachbearing element assembly can comprise a piston and cylinder assembly.

The test assembly can further comprise a plurality of sensors configuredto measure fluid pressure in at least some of the hydraulic bearings.

A hydraulic power source can be provided and coupled to each of thehydraulic bearings to apply pressurized fluid. A controller can beconfigured to provide control signals to selectively pressurize thehydraulic bearings. If desired, the pressure sensors can be configuredto provide input signals to the controller and the controller can beconfigured to ascertain force(s) and/or moment(s) applied to the shaft.For example, the controller can be configured to ascertain forces alonga rotational axis of the shaft and forces along two axes mutuallyorthogonal to each other and to the rotational axis, and moments aboutthe two axes.

The actuator assembly can be configured to apply various forces and/ormoments in up to 5 degrees of freedom with respect to an orthogonalcoordinate system where one axis corresponds to the rotational axis ofthe shaft and for purposes of defining the 5 degrees of freedom,rotation about the rotational axis does not comprise one of the degreesof freedom. For instance, in one embodiment, the first plurality ofhydraulic bearings comprise a first set of hydraulic bearingscircumferentially spaced about the shaft and a second set of hydraulicbearings circumferentially spaced about the shaft, where the second setof hydraulic bearings are axially spaced apart from the first set ofhydraulic bearings on the shaft. Each of the sets of hydraulic bearingsare configured to apply a first lateral force orthogonal to the axis ofrotation and/or a second lateral force orthogonal to the axis ofrotation, and wherein the controller is configured to provide controlsignals to selectively pressurize the first and second sets of hydraulicbearings so as to apply a first moment to the shaft about a first axisorthogonal to the axis of rotation of the shaft. If desired, thecontroller is configured to provide control signals to selectivelypressurize the first plurality of hydraulic bearings so as to apply asecond moment to the shaft about a second axis orthogonal to the axis ofrotation of the shaft and orthogonal to the first axis.

In another embodiment, the actuator assembly includes a supportstructure configured for supporting a second plurality of hydraulicbearings so as to apply an axial force to the shaft, and wherein thetest assembly further comprises a hydraulic power source operablycoupled to each of the hydraulic bearings to apply pressurized fluid. Acontroller is configured to provide control signals to selectivelypressurize the second plurality of hydraulic bearings so as to apply atleast an axial force to the shaft in a first axial direction.

The shaft can include a wide variety of annular surfaces upon which thehydraulic bearings can engage. For example, the shaft can include afirst annular surface about the axis of rotation of the shaft, andwherein the first plurality of hydraulic bearings are configured toengage a portion of the first annular surface that is orthogonal oroblique to the rotational axis of the shaft. The shaft can also includea second annular surface. A second plurality of hydraulic bearings canengage a portion of the second annular surface that is orthogonal oroblique to the rotational axis of the shaft. The controller can beconfigured to provide control signals to selectively pressurize thesecond plurality of hydraulic bearings so as to apply at least a secondaxial force to the shaft in a second axial direction opposite the firstaxial direction. In various embodiments, the first annular surface canface or generally face the second annular surface. Likewise, the firstannular surface and the second annular surface can face or generallyface in opposite directions. In one embodiment, the first annularsurface and the second annular surface can extend radially beyond anouter cylindrical surface of the shaft used to support the shaft forrotation, or be formed by a circumferential groove.

Another embodiment the torque transfer coupling includes a shaft and afirst second set of hydraulic devices. Each hydraulic device of thefirst set of hydraulic devices has a first end operably connected to afirst end of the shaft, wherein the hydraulic devices of the first setof hydraulic devices are disposed about an axis of the shaft. Eachhydraulic device of the second set of hydraulic devices has a first endoperably connected to a second end of the shaft, and wherein thehydraulic devices of the second set of hydraulic devices are disposedabout the axis of the shaft. Each hydraulic device can include a pistonand cylinder assembly wherein extension and retraction of each piston ofeach hydraulic device is generally tangential to a portion of a circleencircling the shaft.

In one embodiment, the torque transfer coupling further includes a firstmember coupled to the first end of the shaft and a second member coupledto the second end of the shaft, wherein each of an end of the firstmember, an end of the second member, the first end of the shaft and thesecond end of the shaft include axially extending surfaces disposedcircumferentially about a respective axis of rotation. The surfaces ofthe first end of the shaft are disposed between surfaces of the firstmember and wherein each hydraulic device of the first set of hydraulicdevices is disposed between opposed facing surfaces of the first memberand the first end of the input shaft, and wherein the surfaces of thesecond end of the shaft are disposed between surfaces of the secondmember and wherein each hydraulic device of the second set of hydraulicdevices is disposed between opposed facing surfaces of the second memberand the second end of the input shaft. If desired, axially extendingsurfaces are formed from slots disposed circumferentially about one ofthe first end of the shaft and the end of the first member, and likewiseabout one of the second end of the shaft and the end of the secondmember.

In one embodiment, each of the hydraulic devices comprises a hydraulicbearing assembly. In another embodiment, each of the hydraulic devicesis single acting having extension under pressure in one direction. Insuch a case, if desired, successive hydraulic devices of each of thefirst set of hydraulic devices and the second set of hydraulic devicesoperate in opposed directions. In another embodiment, each of thehydraulic devices is double acting having extension and retraction underpressure in opposed directions.

If desired, the torque transfer coupling can comprise an elementconfigured to limit axial displacement of the first end of the shaftfrom the end of the first member.

A power source can be configured to provide fluid to operate each of thehydraulic devices, while a controller can be configured to control thepower source. If desired, the controller is configured to operate thehydraulic devices to control stiffness and/or damping of the torquetransfer coupling.

In another embodiment of the invention, a method for applying force andmoment loads to a test specimen is provided. The method includesoperating an actuator assembly to apply force and/or moment loads to anend of a shaft of a wind turbine assembly while the shaft of the windturbine assembly is rotating, the actuator assembly having a shaftsupported for rotation by hydraulic bearings; operating the hydraulicbearings to allow rotation of the shaft of the actuator assembly; andapplying torque to a torque transfer coupling that is connected to theshaft of the actuator assembly. If the torque transfer couplingcomprises a plurality of hydraulic devices, the method can furtherinclude operating the hydraulic devices to transfer torque to the shaftof the actuator assembly while an axis of the shaft of the actuatorassembly moves in five degrees of freedom relative to an axis ofrotation of the torque transfer coupling. Although not to be consideredlimiting, the method is particular advantageous when used for testing awind turbine assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of loads present on a wind turbine assembly.

FIG. 2 is a perspective view of a test assembly for testing a pair ofwind turbine assemblies.

FIG. 3 is a top plan view of a portion of the test assembly of FIG. 2.

FIG. 4 is an elevational view of a portion of the test assembly of FIG.2.

FIG. 5 is an elevational view of a portion of the test assembly of FIG.2.

FIG. 5A is a perspective view of another test assembly.

FIG. 5B is an elevational view of the test assembly of FIG. 5A.

FIG. 6 is a schematic illustration of another test assembly.

FIG. 7 is a front elevational view of the test assembly of FIG. 6.

FIG. 8 is a schematic illustration of a hydraulic bearing assembly.

FIG. 9 is a schematic illustration of two sets of hydraulic bearingassemblies for controlling rotation of a shaft.

FIG. 10 is a schematic illustration of a plurality of hydraulic bearingassemblies used to control a position of a rotating shaft.

FIG. 11 is a schematic illustration of a plurality of hydraulic bearingassemblies.

FIG. 12 is a schematic illustration of a torque transfer coupling.

FIG. 13 is a perspective view of another test assembly.

FIG. 14 is an elevational view of the test assembly of FIG. 13.

FIG. 15 is a perspective view of another test assembly and torquetransfer coupling.

FIG. 16 is a perspective view of another test assembly and torquetransfer coupling.

FIG. 17 is a sectional view of the test assembly of FIG. 16.

FIG. 18 is a top plan view of a portion of the test assembly of FIG. 16.

FIG. 19 is a top plan view of the test assembly of FIG. 16.

FIG. 20 is a perspective view of the torque transfer coupling of FIG.16.

FIG. 21A is a schematic illustration of another test assembly.

FIG. 21B is a sectional view of the test assembly taken along lines21B-21B in FIG. 21A.

FIG. 21C is a perspective view of the test assembly of FIG. 21A withportions removed.

FIG. 22A is a schematic illustration of another test assembly.

FIG. 22B is a sectional view of the test assembly taken along lines22B-22B in FIG. 22A.

FIG. 22C is a perspective view of the test assembly of FIG. 22A withportions removed.

FIG. 23A is a schematic illustration of another test assembly.

FIG. 23B is a sectional view of the test assembly taken along lines23B-23B in FIG. 23A.

FIG. 23C is a perspective view of the test assembly of FIG. 23A withportions removed.

FIG. 24A is a schematic illustration of another test assembly.

FIG. 24B is a sectional view of the test assembly taken along lines24B-24B in FIG. 24A.

FIG. 24C is a perspective view of the test assembly of FIG. 24A withportions removed.

FIG. 25 is an end view of another torque transfer coupling.

FIG. 26 is a sectional view of the torque transfer coupling taken alonglines 26-26 in FIG. 25.

FIG. 27 is an enlarged sectional view of a portion of the torquetransfer coupling of FIG. 25.

FIG. 28 is an enlarged sectional view of a portion of the torquetransfer coupling of FIG. 25.

FIG. 29 is a schematic illustration of an elastomeric bearing.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIGS. 2-8 illustrate a first embodiment of a test assembly 21 fortesting a test specimen such as but not limited to a wind turbineassembly 22 by applying selected force and/or moment loads as describedabove to the wind turbine assembly 22. The test assembly 21 can be usedto simulate or measure force and/or moments loads (which includes torqueon an rotational shaft of the turbine assembly 22) commonly experiencedby the wind turbine assembly 22 in normal operation and/or used toascertain load limits of a wind turbine assembly design.

The wind turbine assembly 22 under test typically includes a drive traincomposed of a gearbox 24, an optional generator 26, and a low speedshaft (LSS) with bearings. An end of the gearbox 24, which can comprisea portion of the hub, or coupled to a hub, or coupled through the lowspeed shaft, is coupled to the test assembly 21. The test assembly 21drives or rotates the drive train while also applying force and/ormoment/torque loads to the end of the drive train. Generally, the testassembly 21 includes a prime mover 28 such as but not limited to anelectric or hydraulic motor with an optional gearbox to obtain thedesired rotations per minute and torque. The prime mover 28 is connectedto a torque transfer coupling 30 that in turn is coupled to an inputshaft 32, or formed part thereof. The input shaft 32 is connected to theend of the drive train in a rigid manner to transfer torque and forcesthereto. An actuator assembly 34 is used to apply forces and/or momentsto the input shaft 32. The torque transfer coupling 30 transfers drivetorque from the prime mover 28 to the actuator assembly 34, while stillallowing movement of the actuator assembly 34 and/or wind turbineassembly 22.

Referring to FIGS. 6-7, input shaft 32 is supported for rotation onhydraulic bearing assemblies 40 and 42 at spaced-apart locations alongthe axis of rotation of the input shaft 32. In the embodimentillustrated, hydrostatic bearings (pressure fed hydrostatic bearings)are described herein by example and will be mentioned below. However, itshould be understood other forms of hydraulic bearings can be used suchas but not limited to pressure balanced sealed bearings, hydrodynamicbearings, spherical roller bearings, etc.

In the exemplary embodiment, hydraulic (e.g. hydrostatic) bearingassemblies 40, 42 are bearing element assemblies 44 spacedcircumferentially or segmented about a surface (e.g. outer surface) ofthe input shaft 32. FIG. 8 illustrates a bearing element assembly 44 indetail. The bearing element assembly 44 includes hydrostatic pad 46supported by an actuator 48. In the exemplary embodiment illustrated,the actuator 48 comprises a fluid actuator having a piston 50 movable ina cylinder 52. If desired, a preload internal spring 53 can be providedand operably connected to the piston 50 and cylinder 52. The piston 50supports the hydrostatic pad 46. The hydrostatic pad 46 supports theinput shaft 32 while it rotates on a thin film of fluid provided to thepad 46 from a flow restricting passageway 56 extending through thepiston 50. The passageway 56 typically extends into the chamber of thecylinder 52. Each cylinder 52 is connected to a support collar orhousing 58. An outer support structure such as a tube 60 (FIG. 6) joinsthe support collars 58 together.

A thrust bearing 62 is also provided for input shaft 32. The thrustbearing 62 sustains axial loads and controls axial movement of inputshaft 32. The thrust bearing 62 can take numerous forms. In oneadvantageous embodiment that has low friction, thrust bearing 62 alsocomprises a segmented hydrostatic assembly with bearing elementassemblies 64 (two of which are illustrated in FIG. 6) disposedcircumferentially about the axis of input shaft 32. Each bearing elementassembly 64 is constructed in a manner similar to bearing assembly 44with piston/cylinder actuators, where a first plurality of bearingelement assemblies 64A include hydrostatic pads configured to face anannular surface 66A and apply force in a first axial direction along theshaft 32, while a second plurality of bearing element assemblies 64Binclude hydrostatic pads configured to face an annular surface 66B andapply force in a second axial direction (opposite the first axialdirection) along the shaft 32, each of the annular surfaces 66A and 66Bbeing about the shaft 32 and in a plane orthogonal to the axis ofrotation of the shaft 32, wherein the annular surfaces face in oppositedirections, herein toward each other. The piston/cylinder assemblies ofthe bearing assemblies 64A and 64B are configured to react axial forcesto a support collar 68. The support collar 68 can be fixedly secured tosupport collar 58 with a support structure such as tube 70.

A controller 80 illustrated in FIG. 6 provides control signals 82 to ahydraulic power source 83 (e.g. pump, accumulators, servo valves, etc.)that in turn is fluidly coupled to each bearing element assembly 44 and64 so as to maintain the position of input shaft 32 in the properposition in spite of loads applied via actuator assembly 34 discussedbelow as well as deflections of the support structure 58, 68, etc,thereby allowing the support structure to be less rigid hence cheaper.

Controller 80 can receive input signals 84 indicative of parameters(e.g. position) of the input shaft 32 as it rotates from suitablesensors 85 (e.g. displacement) and operate in closed-loop control tomaintain the desired position of input shaft 32. Pressure sensors (notshown) can also be provided and operably coupled to measure pressureswithin some or all of the piston/cylinder assemblies in the bearingelement assemblies 44 and 64. Signals from the pressure sensors can beprovided to controller 80 as input signals 86. Controller 80 uses theinput signals 86 to ascertain forces and moments/torque applied to shaft32. The extension and retraction of some or all of the bearing elementassemblies 44 and 64 can be monitored with sensors and provided asinputs to controller 80, if desired, for example to control operation ofeach bearing element assemblies 44 and 64.

In the embodiment illustrated in FIGS. 2-7, the actuator assembly 34includes a plurality of actuators 90 grouped in sets 90A, 90B and 90C,each set 90A, 90B and 90C spaced-apart from each other along the axis ofthe input shaft 32. Referring to FIG. 6, a first set of actuators 90Aare disposed at a first end of shaft 32, for example connected tosupport collar 58 of bearing 40, while a second set of actuators 90B anda third set of actuators 90C are disposed at an end of shaft 32 oppositeof the first set 90A, for example connected to support collar 58 ofbearing 42 and/or support collar 68. Set 90A includes at least twoactuators 100A and 100B (FIG. 7) radially spaced from each other aboutthe axis of shaft 32. As illustrated, additional actuators can beprovided essentially in parallel to each of the actuators 100A and 100B,depending on the amount of force that needs to be applied. Actuators ofsets 90B and 90C are oriented in a manner similar to that of set 90Awherein at least two actuators are radially spaced from each other aboutthe axis of shaft 32. However, the actuators of sets 90B and 90C arealso oriented oblique to the axis of shaft 32 (rather than orthogonal asin set 90A) so that an axial force (F_(X)) can be selectively applied toshaft 32. The controller 80 provides control signals to hydraulic powersource 83 (although a separate hydraulic power source can be provided)so as to operate the actuators of sets 90A, 90B and 90C and generateaxial force F_(X), radial forces F_(Y), F_(Z), and moments about radialaxes orthogonal to the shaft axis, i.e. M_(Y), M_(Z) as desiredincluding two or more loads (forces and/or moments) simultaneously.

It should be noted the configuration of actuators 90 herein describedand illustrated should not be construed as limiting, but rather as anexemplary embodiment wherein other configurations are possible. Forinstance, FIGS. 5A and 5B illustrate another embodiment 21′ whereactuator assembly 34′ comprises sets 90A′, 90B′ and 90C′. In particular,set 90A′ comprises just actuators 100A and 100B, while sets 90B′ and90C′ comprise pairs of parallel operating actuators rather than groupsof three parallel operating actuators.

Another embodiment of an actuator assembly 200 is illustrated in FIG. 9.Actuator assembly 200 is different from actuator assembly 34 in thatsome if not all external actuators 90 are omitted. In this embodiment,selected force and/or moment loads are generated from the bearingelement assemblies 44 and/or 64 (not shown in FIG. 9 but similar to thatillustrated in FIG. 6), which are constructed in a manner similar tothat described above; however, the stroke or travel of each of thepiston/cylinder assemblies is considerably longer. For instance, in oneembodiment, the travel of the piston/cylinder assemblies is in the rangeof 2-3 inches. In a further embodiment, the travel of thepiston/cylinder assemblies is in the range of 3-5 inches. In yet afurther embodiment, the travel of the piston/cylinder assemblies is 5 ormore inches. FIG. 10 schematically illustrates a set of bearing elementassemblies 44 controlling the position of a shaft to be in a centeredposition as indicated by circle 202 or in an offset position asindicated by circle 204. FIG. 11 illustrates hydraulic fluid connectionsto the bearing element assemblies 44 so as to control positioning of theshaft 32. In particular, the bearing element assemblies 44 can behydraulically controlled in opposed sets, herein by way of example foursets; however, more or less sets, or even individual control of eachbearing element assembly 44 can be implemented.

Referring back to FIG. 9, in this embodiment, support collars 58 arefixedly secured to suitable base (not shown). The controller 80 providescontrol signals 102 to hydraulic power source 83 so as to operate thepiston/cylinder assemblies of bearing element assemblies 44 and 64 ofactuator assembly 200 to generate axial (thrust) force F_(X), radial(shear) forces F_(Y), F_(Z), and moments about radial axes orthogonal tothe shaft axis, i.e. M_(Y), M_(Z) as desired including two or more loads(forces and/or moments) simultaneously.

Position sensors 85 (schematically illustrated) can be provided asneeded to monitor the position of shaft 32 and provide correspondinginput signals to controller 80 for position feedback. Position feedbackcan also be provided with suitable sensors measuring the piston/cylinderrelationship of a plurality if not all of the bearing element assemblies44 and 64. As described above, pressure sensors (not shown) can also beprovided and operably coupled to measure pressures within some or all ofthe piston/cylinder assemblies in the bearing element assemblies 44 and64. Signals from the pressure sensors can be provided to controller 80as input signals 86. Controller 80 can use the input signals 86 toascertain forces and moments/torque applied to shaft 32.

Although illustrated in FIG. 9, where the support collars 58 or housingis rigidly secured to a base, in yet another embodiment, externalactuators such as actuators 90 described above can be used incombination with the long stroke bearing element assemblies 44 and 64just described to impart additional load(s) in one or more degrees offreedom in combination with loads generated by bearing elementassemblies 44 and 64.

FIGS. 15-19 illustrate another embodiment of an actuator assembly 250having two pluralities of hydraulic (e.g. hydrostatic) bearingassemblies 252 and 254, each plurality of hydraulic bearing assemblies252, 254 being spaced circumferentially about a surface (e.g. outersurface) of the input shaft 32. However, in this embodiment, thehydraulic bearing assemblies in each plurality 252, 254 are grouped insets (e.g. sets 252A, 252B, 252C and 252D and where plurality 254 aresimilarly grouped), each set acting upon a common shoe 256, which inturn, acts upon the surface of a shaft such as the input shaft 32. Inthe illustrated embodiment, each set comprises two hydraulic bearingassemblies 258; however, this should not be considered required orlimiting wherein one or more hydraulic bearing assemblies can beprovided for each shoe 256. As in the previous embodiment, the sets canbe hydraulically controlled in opposed sets, herein by way of examplefour sets; however, more sets can be used. In addition, depending on thedesired loads to be applied, the number of hydraulic bearing assembliesacting upon each shoe 256 may vary, although the number of hydraulicbearing assemblies for each shoe 256 in each opposed set are typicallythe same. Each shoe includes hydrostatic pads 260 that support the inputshaft 32 while it rotates on a thin film of fluid provided to each padfrom a flow restricting passageway extending through the shoe. Thehydraulic bearing assemblies 258 of each shoe 256 can be configured sothat hydrostatic pads 257 and corresponding thin films are operatingupon the surface of the shoe 256, or as illustrated, upon a surface of asupport structure 264 such as a corresponding support collar 266thereof.

If desired as illustrated, each shoe 256 can further be configured so asto operate as a thrust bearing acting upon annular surfaces 270, 272 ateach end of the input shaft 32. As with the radially orientedhydrostatic pads 260, hydrostatic pads 274 on the side surface of eachshoe 256 supports the input shaft 32 via the annular surface while itrotates on a thin film of fluid provided to each pad 274 from a flowrestricting passageway extending through the shoe 256. A hydraulicbearing assembly or assemblies 280, as illustrated, provide axial forceupon the input shaft 32 via annular surfaces 270, 272. Each of theannular surfaces 270 and 272 is disposed in a plane that is orthogonalto the axis of rotation of the shaft 32 and, herein face each other,although in another embodiment the shoes 256 and hydraulic bearingassemblies 280 can be arranged to engage annular surfaces that face awayfrom each other. The hydraulic bearing assemblies 280 associated witheach shoe 256 can be configured so that hydrostatic pads andcorresponding thin films thereof are operating upon the surface of theshoe 256 or upon a surface of the corresponding support collar 266 orother structure. Sensors and controller can be provided as discussedabove in the previous embodiments to control all the hydraulicassemblies 258 and 280 to provide loads as desired upon the shaft 32 inup to five degrees of freedom.

Yet another actuator assembly 500 for imparting selected forces andmoments to the input shaft 32 is illustrated in FIGS. 13 and 14. In thisembodiment, a disc 502 is coupled to or formed as unitary body with ashaft such as input shaft 32 and a plurality of actuators, inparticular, hydraulic (e.g. hydrostatic) bearing assemblies 504 engagesurfaces of the disc 502 to impart selected forces thereon, and thus,upon input shaft 32. As illustrated, a first set of hydraulic bearingassemblies 506 are configured to engage a first annular surface 502A ofdisc 502, while a second set of hydraulic bearing assemblies 508 areconfigured to engage a second annular surface 502B of disc 502, each ofthe annular surfaces 502A and 502B being disposed in a plane that isorthogonal to the rotational axis of the shaft 32, and face in oppositedirections, herein away from each other. Each of the sets of hydraulicbearing assemblies 506 and 508 include individual hydraulic bearingassemblies 504 spaced apart and disposed about an axis of rotation ofdisc 502. In the embodiment illustrated, the individual hydraulicbearing assemblies 504 are organized in opposed pairs facing each otheron each side of disc 502, which although may simplify operation orcontrol of the hydraulic bearing assemblies to develop selected forcesand/or moments upon disc 502 should not be considered as required orlimiting.

Each of the sets of hydraulic bearing assemblies 506 and 508 includes atleast two spaced apart hydraulic bearing assemblies 504, and commonly,three or more spaced apart hydraulic bearing assemblies, depending onthe desired number of forces and/or moments to be exerted upon disc 502.In a particularly convenient embodiment, each of the sets of hydraulicbearing assemblies 506 and 508 include spaced apart hydraulic bearingassemblies 504 configured to apply opposed forces to each side of thedisc 502 at 90 degree intervals about the axis of rotation of the disc502. In this manner, the hydraulic bearing assemblies 504 can becontrolled to exert thrust loads along the axis of rotation of disc 502as well as exert moments about two axes that are mutually orthogonal toeach other and the axis of rotation of disc 502. It should be noted thattwo or more hydraulic bearing assemblies 504 can be disposed in closeproximity to each other such as at 520 and 522, if for example, momentsabout one axis may be greater than moments about the other axis.

In a further embodiment, a second plurality of actuators, in particular,hydraulic (e.g. hydrostatic) bearing assemblies 530 engagecircumferential surfaces of the rotating shaft such as the input shaft32 as illustrated, or of an element connected thereto such as part ofthe torque transfer coupling 30 or even disc 502. However, at this pointit should be noted that the presence of torque transfer coupling 30 isnot required, but rather is merely an illustrative embodiment.

At least two spaced apart hydraulic bearing assemblies 530, andcommonly, three or more spaced apart hydraulic bearing assemblies,depending on the desired number of forces to be exerted upon input shaft32. In a particularly convenient embodiment, the spaced apart hydraulicbearing assemblies 530 are configured to apply opposed forces to theinput shaft 32 at 90 degree intervals about the axis of rotation of theshaft 32. In this manner, the hydraulic bearing assemblies 530 can becontrolled to exert lateral or shear loads along two axes that aremutually orthogonal to each other and the axis of rotation of inputshaft 32. Like hydraulic bearing assemblies 504, it should be noted thattwo or more hydraulic bearing assemblies 530 can be disposed in closeproximity to each other about the axis of rotation of shaft 32, if forexample, shear forces along one axis may be greater than shear forcesalong the other axis. However, if desired, additional hydraulic bearingassemblies contacting other circumferential rotating surfaces andoperated in parallel with hydraulic bearing assemblies 504 can be usedto exert additional shear forces upon the input shaft 32.

Hydraulic bearing assemblies 504 are actuators as well as bearings andthey impart the force on disk 502 while allowing disk 502 to spin. Useof a disk allows efficient generation of torque loads. Similarly,hydraulic bearing assemblies 530 are actuators as well as bearings andthey impart the force on the input shaft 32, or an element connectedthereto, while allowing input shaft 32, or element connected thereto, tospin. A reaction structure 540 is provided for the hydraulic bearingassemblies 504 and/or 530. A controller, hydraulic power source andposition sensors similar to that described above can be used to controlhydraulic bearing assemblies 504 and/or 530.

Yet further embodiments for imparting selected forces and moments to theinput shaft 32 are illustrated in FIGS. 21A-21C, 22A-22C, 23A-23C and24A-24C. In the actuator assembly 550 illustrated in FIGS. 21A-21C, twoaxially spaced apart pluralities of hydraulic (e.g. hydrostatic) bearingassemblies 552 and 554 are provided. Each of the plurality of hydraulicbearing assemblies 552, 554 have individual hydraulic bearing assembliesspaced circumferentially about a surface (e.g. outer surface) of theinput shaft 32, which can be operated so as to impart linear loads alongand moments about axes orthogonal to the axis of rotation of shaft 32.Two additional sets of hydraulic bearing assemblies 556 and 558 areprovided so as to impart axial loads along the axis of rotation 32. Theindividual hydraulic bearing assemblies of plurality 556 engage anannular surface 559A of shaft 32 that is disposed in a plane orthogonalto the axis of rotation of shaft 32. Likewise, the individual hydraulicbearing assemblies of plurality 558 engage annular surface 559B of shaft32 that is disposed in a plane that orthogonal to the axis of rotationof shaft 32, where the surfaces 559A and 559B face in oppositedirection, herein where the surface 559A faces surface 559B. A suitablesupport structure 557 is provided as a reaction structure for each ofthe hydraulic bearing assemblies (omitted in FIG. 21C for purposes ofshowing each of the plurality of hydraulic bearing assemblies 552, 554).

The actuator assemblies 560 and 570 of FIGS. 22A-22C and FIGS. 23A-23C,respectively, each include two pluralities of hydraulic (e.g.hydrostatic) bearing assemblies 562 and 564 wherein each of theindividual hydraulic bearing assemblies of the pluralities 562 and 564is configured or oriented so as to impart a load that is oblique to therotational axis of the shaft 32. Generally, the plurality of hydraulicbearing assemblies 562 engage an annular surface 568A generally facingan annular surface 568B upon which the plurality of hydraulic bearingassemblies 564 engage. In the embodiment of FIGS. 22A-22C each of thesurfaces 568A and 568B have curved or rounded conical surfaces (curvedor rounded particularly when viewed in cross-section taken along theaxis of rotation of shaft 32), while surfaces 569A and 569B are conicalhaving relatively straight surfaces in cross-section taken along theaxis of rotation of shaft 32. Each of the hydraulic bearing assemblies562 and 564 contact a surface portion of each corresponding annularsurface that can be considered oblique to the rotational axis of shaft32. A suitable support structure 567 is provided as a reaction structurefor each of the hydraulic bearing assemblies (omitted in FIGS. 22C and23C for purposes of showing each of the plurality of hydraulic bearingassemblies 562, 564). An advantage of the embodiments of FIGS. 22A-22Cand FIGS. 23A-23C is the reduced number of hydraulic bearing assemblies(herein by way of example eight in total) that are necessary to provideloads and/or displacements of shaft 32 in 5 degrees of freedom.

In the embodiment of FIGS. 24A-24C, the hydraulic bearing assemblies ofthe plurality 564 are displaced as a set, such as by 45 degrees,relative to the hydraulic bearing assemblies of the plurality 562. Inthis manner, the surfaces 568A and 569B can be disposed axially closertogether to form a more compact assembly. A suitable support structure577 is provided as a reaction structure for each of the hydraulicbearing assemblies (omitted in FIGS. 22C and 23C for purposes of showingeach of the plurality of hydraulic bearing assemblies 562, 564).Elements or portions of the hydraulic bearing assemblies of pluralities562 and 564 may even overlap each other when viewed in a cross-sectiontaken along the axis of rotation of shaft 32. Such a technique can beused if desired in any of the actuator assemblies herein discussed.

It should be noted that each plurality of hydraulic bearing assemblies552, 554, 562 and 564 typically comprises three or more. In addition,although illustrated where the surfaces 558A and 558B, 568A and 568B,and 569A and 569B generally face each other, it should be understood thesurfaces can be oriented so as to generally face away from each other,if desired, where the plurality of hydraulic bearing assemblies 552,554, 562 and 564 are then arranged to accordingly.

The torque transfer couplings herein described are useful intransferring torque and other loads while allowing movement ofassemblies connected to opposite ends thereof. Therefore, it should beunderstood the torque transfer couplings herein described are notlimited to wind turbine testing, which is provided herein as anexemplary application.

As indicated above, the torque transfer coupling 30 probably bestillustrated in FIG. 5 transfers drive torque from the prime mover 28 tothe actuator assembly 34, while still allowing movement of the actuatorassembly 34 and/or wind turbine assembly 22. In the embodimentillustrated, the torque transfer coupling 30 includes a shaft, e.g.solid or tubular, herein a tube 300 (hereinafter “torque tube”) and twosets of circumferentially arranged hydraulic devices, which can includepiston and cylinder assemblies where extension and retraction of eachpiston generally is tangential to a portion of a circle encircling thetorque tube 300. In coupling 30, the hydraulic devices comprise doubleacting actuators. A first set of actuators 302 connects the torque tube300 to the prime mover 28 and a second set of actuators 304 connects thetorque tube 300 to an actuator assembly such as any of the actuatorassemblies herein discussed. Referring to the first set of double actingactuators 302, each actuator has a first end 306, such as a piston rod,pivotally joined to the prime mover 28, while a second end 308 of eachactuator, such as the cylinder assembly, is pivotally joined to thetorque tube 300. If desired, connection of the piston rod and cylinderassemblies to the prime mover 28 and torque tube can be reversed. Theactuators 302 are circumferentially disposed about the axis of rotationof the torque tube 300 in manner such that extension and retraction ofthe piston rod of each actuator relative to its corresponding cylinderis generally tangential to a portion of a circle encircling the torquetube 300. The second set of actuators 304 is connected to torque tube300 and actuator assembly 34 and 200 in a manner similar to the firstset of actuators 302. In the exemplary embodiment, the actuators in sets302 and 304 are operated from controller 80 and hydraulic power source83 (although a separate controller and/or hydraulic power source can beprovided if desired) so as to extend and retract in a manner asnecessary while rotating with torque tube 300 such that compensation isprovided that allows the axis of rotation of torque tube 300 to bedisplaced, if necessary, from the axes of rotation of input shaft 32and/or the prime mover 28. Hydraulic slip ring(s) not shown can beprovided to provide hydraulic fluid to each of the actuators in sets 302and 304. Pressure sensors (not shown) can also be provided and operablycoupled to measure operating pressures of some or all of the actuatorsin set 302 and/or set 304, wherein output signals from the pressuresensors can then be provided to controller 80 and used to ascertain theapplied torque M_(X). The extension and retraction of some or all of theactuators in sets 302 and 304 can be monitored with sensors and providedas inputs to controller 80, if desired. Likewise, linear and/orrotational position sensors can also be operably configured to sense theposition of the input shaft 32, torque tube 300 and/or shaft of the windturbine under test in one, some or all degrees of freedom and provideposition signals to the controller 80 during operation.

The torque transfer coupling 30 will be nominally controlled such thatthe rotational position of the shaft 32 and shaft of the wind turbineassembly under test are maintained at a desired angle relative to oneanother, which may be static or which may vary in time. However,torsional systems often have difficulties due to resonances that aredirectly affected by the stiffness and damping characteristics of thecoupling. Since the torque transfer coupling 30 is actively controlled,it is possible to command the hydraulic devices of the torque transfercoupling 30 in such a manner as to add additional stiffness or dampingto the torque transfer coupling 300.

By manual or automatic analysis, the system dynamics can be used todetermine whether additional stiffness and/or damping would be abenefit. Likewise, controller 80 can use a compensation signal orparameter to achieve the desired stiffness or damping. For instance,from suitable sensors (e.g. torque cells, pressure sensors or the like),a compensation signal or parameter can be computed from the measured orascertained input torque versus the torque desired. This signal orparameter can be used as a basis alone or in part for operating thepower source 83 so as to control the hydraulic devices 302 and 304accordingly so as to command relative motion between the various shaftsof the torque transfer coupling 30 such that the coupling and/or shaftdynamic characteristics change as desired. An example of such acompensation signal is a damping term which, in the presence of asinusoidal torque input, would have a phase lag of 90° with respect tothe torque signal and would thereby add damping to the dynamic system.Various combinations of damping and stiffness terms are possible bothfor sinusoidal and non-sinusoidal input torques.

It should also be noted that the actuators in each set 302 and 304 canbe connected together hydraulically to minimize hydraulic flowrequirements.

Although the control system components and operation thereof has beendescribed with respect to torque transfer coupling 30, it should benoted the control system and operation thereof can be used with any ofthe torque transfer couplings herein described

FIG. 12 illustrates a portion of another torque transfer coupling 400also comprising circumferentially arranged sets of hydraulic devices,one set at each end of torque tube 300, wherein each hydraulic devicecan include a piston and cylinder assembly and wherein extension andretraction of each piston is generally tangential to a portion of acircle encircling the torque tube 300.

By way of example in FIG. 12 the hydraulic devices 402 couple torquetube 300 to actuator assembly 34 (input shaft 32); however, it should beunderstood a second set of similar hydraulic devices can be provided tocouple the torque tube 300 to primer mover 28. As illustrated, the inputshaft 32 and the torque tube 300 include axially oriented projections(dogs) that overlap each other in the axial direction of torque tube300. Specifically, projections 404 are rigidly joined to or are a partof input shaft 32, while projections 406 are rigidly joined to or are apart of tube 300. The hydraulic devices 402 are arranged such that ahydraulic device is interposed between each pair of overlappingprojections 404 and 406. Each hydraulic device can comprise ahydrostatic bearing element assembly (similar to bearing elementassemblies 44) having a pad supporting the associated projection via athin film of fluid as described above. (It should be understood theother types of bearings described above can also be used). In a furtherembodiment, the piston/cylinder assemblies of each pair of hydraulicdevices are oriented between each pair of projections 404 and 406 so asto operate (extend and retract) in opposite directions. In FIG. 12,arrows 408 represent extension of each piston of each correspondinghydraulic device. In this manner, one set (every other hydraulic devicecircumferentially about tube 300) react positive torque about tube 300,while a second set (the hydraulic devices interposed between thehydraulic devices of the first set) react negative torque about tube300. Like the actuators of torque transfer coupling 30, the hydraulicdevices 402 of torque transfer coupling 400 can be individuallycontrolled and/or can be connected together hydraulically minimizehydraulic flow requirements.

Referring back to FIGS. 5A and 5B, torque transfer couplings 400′ and400″ are illustrated and are similar in construction and function totorque transfer coupling 400. In transfer couplings 400′ and 400″,overlapping projections 404′ and 406′ are present where each projection406′ is disposed in a slot 405 and where the material between thesuccessive slots 405 form each of the projections 404′. In theembodiment of FIGS. 5A and 5B, hydraulic devices 402 (e.g. hydrostaticbearings) are configured as a plurality (herein by example two) ofparallel operating actuators 407 (FIG. 5B) between each of theprojections 404′ and 406′.

FIGS. 25-28 illustrate yet another torque transfer coupling 400′″similar in construction and function to torque transfer couplings 400,400′ and 400″. As in the previously discussed embodiments overlappingprojections 404′ and 406′ are present where each projection 406′ isdisposed in a slot 405. In this embodiment, projections 406′ compriseblock members 415 secured to tube 300 (herein using fasteners 417),while projections 404′ form collar assemblies 425 at each end of thetube 300, the collar assemblies 425 being fixedly connected to the inputshaft 32 at one end and to the prime mover 28 at the other end.Generally, each collar assembly 425 includes a mounting plate 427,spacers 429 and a ring plate 431. Ring plate 431 includes an aperture433 through which tube 300 extends when each of the block members 415are disposed in a corresponding slot 405 formed by spacers 429.Fasteners 435 secure the ring plate 431 and spacers 429 to the mountingplate 427. In a manner, similar to transfer couplings 400′ and 400″,generally hydraulic devices 402 (e.g. hydrostatic bearings) are disposedbetween the block members 415 and spacers 429 so as to react positiveand negative torque and allow movement of the collar assemblies 425relative to tube 300. In FIG. 27, which corresponds to collar assembly425 on end 441 of tube 300, the hydraulic devices 402 comprisepiston/cylinder assemblies similar to transfer couplings 400′ and 400″where each piston 443 slides upon a flat bearing surface 445. However,in FIG. 28, which corresponds to collar assembly 425 on end 447 of tube300, the hydraulic devices 402 comprise piston/cylinder assemblies thatprovide increased angular movement between the collar assembly 425 andtube 300. Although the piston 443 slides upon a flat bearing surface445, the cylinder that is pressurized for the piston 443 is formed in asocket member 449 that can move relative to block member 415 in a socket450. For instance, socket member 449 can form a hydraulic bearing (e.g.hydrostatic bearing) with respect to socket 450 in block member 415.

Another torque transfer coupling is illustrated in FIGS. 15, 16, 19 and20 at 600. Torque transfer coupling 600 includes beams 602 and 604. Beam602 can be coupled to input shaft 32 to rotate therewith, while beam 604can be coupled to a prime mover or a shaft of the turbine under test.Each beam 602,604 includes support structures 605 at each end. Disposedbetween beams 602,604 is a cruciform or intermediate member 606. Thecruciform 606 includes four support structures 607 spaced about an axisof rotation at equal angular intervals. As illustrated, the supportstructures 607 of the cruciform 606 cooperate with the supportstructures 605 of the beams 602, 604 to least partially restrain the(i.e. for radial displacement of the cruciform 606 relative to the axisof rotation). In the embodiment illustrated, opposed hydraulic bearingassemblies 610 (e.g. hydrostatic assemblies) couple the supportstructures 607 of the cruciform 606 to the corresponding supportstructures 605 of each end of each respective beam 602, 604. In theembodiment illustrated, the support structures 605 of the beams 602, 604comprise brackets with spaced-apart bracket flanges 612, while thesupport structures 607 of the cruciform 606 each comprise a projectionwith a projection surface 612 facing each bracket flange 610. Ahydraulic bearing assembly 620 is disposed between each projectionsurface 612 and each corresponding bracket flange 610. It should benoted that the support structures 607 of the cruciform 606 can comprisespaced-apart bracket flanges, and the support structure 605 of each beam602, 604 can include a projection with a projection surface facing eachbracket flange. The hydraulic bearing assemblies 620 can be configuredto provide two dimensional compliance by providing a thin film onsurfaces of the bracket flanges 610 or the projection surfaces 612 in amanner similar to the hydraulic bearing assemblies described above.Relative two dimensional movement of the bracket flanges 610 andcorresponding projection surfaces 612 allows the axis of rotation of thebeam 602 to be at an angle or otherwise offset relative to the axis ofrotation of the beam 604 while still effectively transferring torquethrough the coupling 600.

It should be noted that an additional mechanism such as pilotbearing(s), mechanical linkage and/or spring(s) (schematically indicatedby element 312 in FIG. 5) can be provided to couple the torque tube 300and actuator assembly 34 and/or prime mover 28 axially together so as toprovide axial restraint for torque tube 300 or for any of torquetransfer couplings 30, 400, 400′, 400″ or 600. Exemplary pilot bearingsare illustrated in FIG. 26 at 451. In this embodiment, a spindle 453 issecured to each mounting plate 427, while a plate member 455 is securedto each end of tube 300. A bearing assembly 457 operably couples thespindle 453 to the plate member 455 so as to provide axial restraint butincludes cooperating bearing elements that allow the desired tiltingmovement of the collar assembly 425 relative to the tube 300.

It should be noted that the axial restraint is typically provided ononly one coupling, while the other is free axially. The pilot bearingsalso serve to fix the XY (lateral and vertical) motion of the shaftportions on each coupling. While this mechanism is not required for allembodiments herein described, in its absence, additional controlchannels may be needed to hold the centerlines of the shaft portions ata fixed position relative to one another.

FIG. 29 illustrates an elastomeric bearing 700 that can be used in placeof the hydraulic devices in the torque transfer couplings describedabove. Generally, the elastomeric bearing 700 comprises a first portion702 comprising alternating layers of relatively thin layers ofelastomeric material and rigid plates bonded or laminated together. Asused herein “thin” is defined as a layer of thickness of the elastomericmaterial that is not substantially extruded from portion 702 orotherwise damaged under the compressive load requirements that theelastomeric bearing 700 is expected to carry. The first portion 702provides the elastomeric bearing 700 with shear compliance.

The second portion 704 is secured to the first portion 702 with a rigidsupport plate 706. The second portion 704 comprises a thicker layer ofelastomeric material (thick enough so as to allow relative pivotalmovement between support surface 708 and 710). The second portion 704 isdisposed in a recess or otherwise is annularly surrounded by walls 714of a housing or mount 712, the inner surfaces of the walls 714 of whichslidably engage the rigid support plate 706. As indicated above, theelastomeric material of the bearing 700 can be compressed or otherwisedeformed in the presence of compressive loads upon the bearing 700. Thetype of elastomeric material and its thickness in portion 704 areselected such that when the bearing 700 is compressed, the elastomericmaterial in portion 704 extrudes to engage the surfaces of the walls714, possibly filling an annular recess 718 if provided. Particularly inthis state, the second portion is compliant for bending motions allowingrelative pivotal motion between support surfaces 208, 210. It should benoted the shape of the portions 702, 704, housing 712 can take anyconvenient form such as but not limited to cylindrical or rectangularforms.

Although the subject matter has been described in a language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above ashas been determined by the courts. Rather, the specific features andacts described above are disclosed as example forms of implementing theclaims.

1. A test assembly comprising: a prime mover; an actuator assemblyhaving an end configured to be attached to a test specimen shaft of atest specimen, the actuator assembly having a shaft; a first pluralityof hydraulic bearings configured to support the shaft of the actuatorassembly for rotation; and a torque transfer coupling connecting theprimer mover to the actuator assembly.
 2. The test assembly of claims 1wherein the actuator assembly includes a support structure forsupporting each of the hydraulic bearings and actuators connected to thesupport structure and arranged to apply forces and/or moments to theinput shaft.
 3. The test assembly of claims 1 wherein the actuatorassembly includes a support structure for supporting each of thehydraulic bearings and wherein the hydraulic bearings comprise aplurality of bearing element assemblies disposed circumferentially aboutthe shaft.
 4. The test assembly of claim 3 wherein each bearing elementassembly comprises a piston and cylinder assembly, and the test assemblyfurther comprises a plurality of sensors configured to measure fluidpressure in at least some of the bearing element assemblies.
 5. The testassembly of claim 4 and further comprising a hydraulic power sourceoperably coupled to each of the piston and cylinder assemblies to applypressurized fluid and a controller configured to provide control signalsto selectively pressurize the piston and cylinder assemblies.
 6. Thetest assembly of claim 5 wherein the pressure sensors are configured toprovide input signals to the controller and the controller is configuredto ascertain force(s) and/or moment(s) applied to the shaft.
 7. The testassembly of claim 6 wherein the controller is configured to ascertainforces along a rotational axis of the shaft and forces along two axesmutually orthogonal to each other and to the rotational axis, andmoments about the two axes.
 8. The test assembly of claims 1 wherein theactuator assembly includes a support structure for supporting each ofthe hydraulic bearings and wherein the hydraulic bearings are configuredto apply forces and/or moments to the input shaft.
 9. The test assemblyof claim 8 and further comprising a hydraulic power source operablycoupled to each of the hydraulic bearings to apply pressurized fluid anda controller configured to provide control signals to selectivelypressurize the first plurality of hydraulic bearings so as to apply afirst lateral force in a first lateral direction orthogonal to an axisof rotation of the shaft.
 10. The test assembly of claim 9 wherein thefirst plurality of hydraulic bearings are configured to apply a secondlateral force in a direction orthogonal to both the first lateraldirection and the axis of rotation of the shaft, and wherein thecontroller is configured to provide control signals to selectivelypressurize the hydraulic bearings so as to apply the first lateral forceand/or the second lateral force.
 11. The test assembly of claims 1wherein the first plurality of hydraulic bearings comprise a first setof hydraulic bearings circumferentially spaced about the shaft and asecond set of hydraulic bearings circumferentially spaced about theshaft, the second set of hydraulic bearings being axially spaced apartfrom the first set of hydraulic bearings on the shaft, wherein each ofthe sets of hydraulic bearings are configured to apply a first lateralforce orthogonal to the axis of rotation and/or a second lateral forceorthogonal to the axis of rotation, and wherein the controller isconfigured to provide control signals to selectively pressurize thefirst and second sets of hydraulic bearings so as to apply a firstmoment to the shaft about a first axis orthogonal to the axis ofrotation of the shaft.
 12. The test assembly of claim 11 wherein thecontroller is configured to provide control signals to selectivelypressurize the first plurality of hydraulic bearings so as to apply asecond moment to the shaft about a second axis orthogonal to the axis ofrotation of the shaft and orthogonal to the first axis.
 13. The testassembly of claim 1 wherein the actuator assembly includes a supportstructure configured for supporting a second plurality of hydraulicbearings so as to apply an axial force to the shaft, and wherein thetest assembly further comprises a hydraulic power source operablycoupled to each of the hydraulic bearings to apply pressurized fluid anda controller configured to provide control signals to selectivelypressurize the second plurality of hydraulic bearings so as to apply atleast an axial force to the shaft in a first axial direction.
 14. Thetest assembly of claim 13 wherein the shaft includes a first annularsurface about the axis of rotation of the shaft, and wherein the firstplurality of hydraulic bearings are configured to engage a portion ofthe first annular surface that is orthogonal or oblique to therotational axis of the shaft.
 15. The test assembly of claim 14 whereinthe shaft includes a second annular surface about the axis of rotationof the shaft, wherein the support structure is configured for supportinga second plurality of hydraulic bearings to engage a portion of thesecond annular surface that is orthogonal or oblique to the rotationalaxis of the shaft, and wherein the controller is configured to providecontrol signals to selectively pressurize the second plurality ofhydraulic bearings so as to apply at least a second axial force to theshaft in a second axial direction opposite the first axial direction.16. The test assembly of claim 15 wherein the first annular surfacefaces the second annular surface.
 17. The test assembly of claim 16wherein the first annular surface and the second annular surface face inopposite directions.
 18. The test assembly of claim 17 wherein the firstannular surface and the second annular surface extend radially beyond anouter cylindrical surface of the shaft used to support the shaft forrotation.
 19. The test assembly any one of claims 1 wherein the torquetransfer coupling comprises: a shaft; a first set of hydraulic devices,each hydraulic device of the first set of hydraulic devices having afirst end connected to the shaft and a second end connected to the primemover; and a second set of hydraulic devices, each hydraulic device ofthe second set of hydraulic devices having a first end connected to theshaft and a second end connected to the actuator assembly.
 20. The testassembly of claim 19 wherein each hydraulic device comprises a piston,and wherein the hydraulic devices of the first set of hydraulic devicesare circumferentially disposed about an axis of the shaft whereinextension and retraction of a piston of each hydraulic devices isgenerally tangential to a portion of a circle encircling the shaft. 21.The test assembly of claim 20 wherein the hydraulic devices of thesecond set of hydraulic devices are circumferentially disposed about anaxis of the shaft wherein extension and retraction of a piston of eachhydraulic device is generally tangential to a portion of a second circleencircling the shaft.
 22. A test assembly comprising: a prime mover; anactuator assembly having an end configured to be attached to a testspecimen shaft of a test specimen, the actuator assembly having a shaft,the shaft having a circumferential surface and first and second annularsurfaces that are disposed in planes arranged to intersect with arotational axis of the shaft; a first plurality of hydraulic bearingsconfigured to support the shaft of the actuator assembly for rotationabout the rotational axis; a second plurality of hydraulic bearingsconfigured to engage the first annular surface; and a third plurality ofhydraulic bearings configured to engage the second annular surface. 23.The test assembly of claims 22 wherein the first plurality of hydraulicbearings comprise a first set of hydraulic bearings circumferentiallyspaced about the shaft and a second set of hydraulic bearingscircumferentially spaced about the shaft, the second set of hydraulicbearings being axially spaced apart from the first set of hydraulicbearings on the shaft, wherein each of the sets of hydraulic bearingsare configured to apply a first lateral force orthogonal to the axis ofrotation and/or a second lateral force orthogonal to the axis ofrotation, and wherein the controller is configured to provide controlsignals to selectively pressurize the first and second sets of hydraulicbearings so as to apply a first moment to the shaft about a first axisorthogonal to the axis of rotation of the shaft.
 24. The test assemblyof claim 23 wherein the controller is configured to provide controlsignals to selectively pressurize the first plurality of hydraulicbearings so as to apply a second moment to the shaft about a second axisorthogonal to the axis of rotation of the shaft and orthogonal to thefirst axis.
 25. A method for applying force and moment loads to a testspecimen, comprising: operating an actuator assembly to apply forceand/or moment loads to an end of a shaft of a wind turbine assemblywhile the shaft of the wind turbine assembly is rotating, the actuatorassembly having a shaft supported for rotation by hydraulic bearings;operating the hydraulic bearings to allow rotation of the shaft of theactuator assembly; and applying torque to a torque transfer couplingthat is connected to the shaft of the actuator assembly.
 26. The methodof claim 25 wherein the torque transfer coupling comprises a pluralityof hydraulic devices, the method further comprising operating thehydraulic devices to transfer torque to the shaft of the actuatorassembly while an axis of the shaft of the actuator assembly moves infive degrees of freedom relative to an axis of rotation of the torquetransfer coupling.
 27. The method of claims 25 wherein the test specimencomprises a wind turbine assembly.